Ever more stringent regulations regarding permissible pollutant emissions by motor vehicles fitted with internal combustion engines make it necessary to keep the pollutant emissions as low as possible during operation of the internal combustion engine. One of the ways in which this can be done is by reducing the emissions which occur during the combustion of the air/fuel mixture in the relevant cylinder of the internal combustion engine. Another is to use waste gas handling systems in internal combustion engines which convert the emissions which are generated during the combustion process of the air/fuel mixture in the relevant cylinder into harmless substances. Catalyzers are used for this purpose, which convert carbon monoxide, hydrocarbons and nitrous oxide into harmless substances. Both the explicit influencing of the generation of the pollutant emissions during the combustion and also the conversion of the pollutant components with a high level of efficiency by an exhaust gas catalyzer require a very precisely set air/fuel ratio in the respective cylinder.
The later published patent application DE 103 04 245 B3 discloses a method for adapting signal sampling of Lambda probe signal values for use in a cylinder-selective Lambda control for a multi-cylinder internal combustion engine. A Lambda probe records the oxygen values in the waste gas for individual cylinders in the waste gas tract at predefined points in time. From the Lambda values measured in this way for individual cylinders control deviations for the cylinders are reconstructed from which a characteristic value is computed. The times for measuring the Lambda values of the individual cylinders are related to the crankshaft angle such that the characteristic value assumes an extreme value.
A method for cleansing waste gas is known from US 2003/0014967 A1 in conjunction with a waste gas system. A gas sensor is arranged so that it is subjected to a passing stream of waste gas and this occurs in chronological sequence from the respective cylinders. A time characteristic of the sensor signal includes information about the air/fuel ratio of the individual cylinders (see paragraph 0012). A control device can also comprise a cylinder-selective injection system with which the air/fuel ratio can be individually adapted to the individual cylinders. To this end the injection time is influenced in a cylinder-selective manner. From US 2002/0139354 A1 (D2) controlling a simultaneous injection of fuel into all cylinders after the start of the internal combustion engine is known. A cylinder identification means is provided to identify the individual cylinders based on the crankshaft angle and in this case to generate a cylinder identification signal. A fuel dispensing control means to control the fuel injection valves of the individual cylinders is provided, based on the crankshaft angle signal. A fuel injection volume correction means is provided for correcting the activation periods of the injection valves.
From the Patent Abstracts of Japan for JP 57 140 529 A method for deactivation of cylinders in an internal combustion engine with a plurality of cylinders is known in which for a down shift of a gear a check is made as to whether fuel supply is to be suppressed to all cylinders or merely to one cylinder group.
U.S. Pat. No. 4,495,924 discloses a fuel injection control system with means for computing an injection start in relation to a crankshaft angle and for computing the duration of the fuel-injection. An injection signal means is provided for each cylinder to generate an injection signal which increases at the point of the computed start time of the injection and which has a duration which corresponds to the computed duration of the fuel injection.
A method is known from US 2003/0110845 A1 for detecting misfires, and this is done for each cylinder. For a cylinder with misfires the fuel delivery is suppressed. An error in the mechanism is determined if a parameter based on the oxygen concentration indicates a richer value of the current air/fuel mixture of the waste gas than a predefined reference value makes this.
A method is known from US 2002/0088446 in which an air/fuel ratio detection period is predefined in relation to an air/fuel ratio sensor which includes waste gas packets of all cylinders. Depending on a peak value phase, which is maximized on a rich or a lean side, induced by variations of the air/fuel ratio, a cylinder is determined, in which the air/fuel ratio is to be corrected and the fuel delivery is adapted accordingly.
A method is know from DE 102 06 402 C1, in which for a global Lambda setpoint, which is provided for all cylinders, the excitation amplitude is added to one of the cylinders. A first injection correction for the cylinder is computed from the excitation time. The added Lambda value is delayed and/or filtered and subtracted as Lambda setpoint value for the cylinder from the actual Lambda value for the cylinder. The difference is applied as control deviation to a Lambda controller which determines a second injection correction for the cylinder.
WO 90/02874 discloses a method for detecting misfires of an internal combustion engine with a plurality of cylinders, in which the output voltage of a Lambda sensor is monitored in the exhaust system and compared with a reference voltage. A deviation of the difference between the sensor and the reference voltage from an expected value is signaled as a misfire in at least one of the cylinders. An expected gas delay time is determined as a function of an empirically determined engine map which is stored on a computer.
A method for a multi-cylinder internal combustion engine for cylinder-selective controlling of an air/fuel mixture to be burnt is known from DE 199 03 721 C1, in which the Lambda values for different cylinders or cylinder groups are sensed and controlled separately. To this end a probe evaluation unit is provided, in which a time-triggered evaluation of the waste gas probe signal is undertaken and thus a cylinder-selective Lambda value for each cylinder of the internal combustion engine determined. Each cylinder is assigned an individual controller which is embodied as a PI or PID controller and for which the control variable is a cylinder-individual Lambda value and of which the guide variable is a cylinder-individual setpoint value of the Lambda. The manipulated variable of the relevant controller then influences the injection of the fuel into the relevant assigned cylinder.
The quality of the cylinder-individual Lambda regulation is decisively dependent on how precisely the measuring signal of the waste gas probe is assigned to the waste gas of the relevant cylinder. During the operation of the waste gas probe its response behavior can change and thus also the degree of precision of the assignment of the measuring signal of the waste gas probe to the waste gases of the respective cylinder.